1. Field of the Invention
The present invention relates to a load sensor, a load sensor unit, and an insertion detection device.
2. Description of the Related Art
A technique is available for a load sensor mounted within an automobile seat, such as a driver""s seat, for detecting the presence of a seated person. An example, conventional load sensor of this type is shown in FIG. 52.
In the example, pressure sensors A1 to A4, B1 to B4, C1 to C4, D1 to D4 and E1 to E4 are located at the intersections of vertical axes 1 to 4 and horizontal axes A to E in a sheet S disposed within a seat. A controller 5 determines from pressure detection results, provided by the pressure sensors A1 to A4, B1 to B4, C1 to C4, D1 to D4 and E1 to E4, whether the seat is bearing a load, and transmits the load determination results to a predetermined driver 6. Pressure sensitive conductive material, having a resistance that varies in accordance with the pressure applied, is employed for the pressure sensors A1 to A4, B1 to B4, C1 to C4, D1 to D4 and E1 to E4.
For the load sensor in FIG. 52, the pressure sensors A1 to A4, B1 to B4, C1 to C4, D1 to D4 and E1 to E4, made of pressure sensitive conductive material, must be arranged as a matrix. Further, in order to detect pressure imposed at various points on the sheet S, multiple pressure sensors, A1 to A4, B1 to B4, C1 to C4, D1 to D4 and E1 to E4, are required. Thus, the resulting circuit is complicated, and the manufacturing costs are increased.
It is, therefore, one objective of the present invention to provide a load sensor, having a comparatively simple and inexpensive configuration and circuit structure, that can easily and accurately detect loads.
To achieve the above object, it is characterized by comprising:
an elastic tube, at least one part of which, in the circumferential direction, is a conductive portion;
an elongated insertion member that has longitudinally arranged first and second electrode members provided at a distance, and that is inserted into the elastic tube; and
envelope members that are provided longitudinally, at a predetermined distance, to enclose the insertion member, and that, together with the insertion member, are inserted into the elastic tube to separate the insertion member from the elastic tube,
wherein, while the elastic tube is in the normal state, the first and the second electrode members are so positioned, at a distance from the conductive portion of the elastic tube, that when an external load bends the elastic tube an electrical connection is established between the first and the second electrode members, with or without the conductive portion of the elastic tube.
Further, to achieve the objective, it is characterized by comprising:
an elastic tube, at least one part of which, in the circumferential direction, is a conductive portion;
an elongated insertion member that has longitudinally arranged electrode members provided at a distance, and that is inserted into the elastic tube; and
envelope members that are provided longitudinally, at a predetermined distance, to enclose the insertion member, and that, together with the insertion member, are inserted into the elastic tube to separate the insertion member from the elastic tube,
wherein, while the elastic tube is in the normal state, the electrode members are so positioned, at a distance from the conductive portion of the elastic tube, that when an external load bends the elastic tube an electrical connection is established between the electrode members and the conductive portion of the elastic tube, with or without the conductive portion of the elastic tube.
Preferably, for the envelope members, at least, one of the separating interval, the thickness, and the width in the longitudinal direction is set in accordance with the magnitude of the load that is to be detected.
Preferably, the envelope members are formed of insulating material.
Further, it is preferable that the envelope members be ring-shaped and externally engage the outer wall of the insertion member.
It is preferable that the envelope members be secured to the insertion member by an adhesive.
Preferably, the envelope members are thermally shrinking tubes.
Preferably, the envelope members are formed by winding insulating tape around the insertion member.
Preferably, the insulating tape is spirally and continuously wound around the insertion member in the longitudinal direction with a predetermined gap.
It is preferable that the envelope members each include a metal fixing member, attached via a predetermined insulating member to the outer wall of the insertion member, and a coated insulating member, fixed to and covering the outer wall of the metal fixing member.
It is preferable that the envelope members each include a metal fixing member, attached to the outer wall of the insertion member, and a coated insulating member, fixed to and covering the outer wall of the metal fixing member.
It is preferable that the insertion member includes, on the outer wall on which the first and the second electrode members are provided, the first and the second electrode members and an elastic insulating member.
Preferably, the load sensor further comprises a signal extraction output line that is electrically connected to the conductive portion of the elastic tube when the conductive portion, wound around the outer walls of the envelope members, is inserted into one end of the elastic tube.
In addition, preferably, the electrode members are formed of elastic conductive members through which hollow, longitudinal portions passes.
It is preferable that the conducive members be made of an elastic conductive material, a conductive metal, a compound material composed of an elastic conductive material and a conductive metal, or a compound material composed of a conducive metal and an insulating material.
It is preferable that the load sensor further include an exterior elastic tube enclosing the elastic tube.
Further, it is preferable that the load sensor include a load sensor body incorporating the elastic tube, the insertion member and the envelope member, and a substantially plate-shaped base member whereon the load sensor body is mounted.
It is preferable that the load sensor include a load sensor body incorporating the elastic tube, the insertion member and the envelope member, and two plate-shaped pressing members for vertically sandwiching and securing the load sensor body.
It is preferable that the electrode members be fashioned from flexible members, and that the electrode members constitute the insertion member.
Preferably, the electrode members have metal, longitudinally laid lines.
Preferably, the electrode members each include an elongated flexible core member and a metal line wound coil-like around the outer wall of the core member.
It is preferable that the core member be an insulating member of resin, rubber or a fibrous material, or a compound material incorporating several of these materials.
Preferably, the core member is formed of an elastic material, and the metal line is wound around and embedded in the outer wall of the core member.
It is preferable that a spiral groove into which the metal line is to be fitted is formed in the outer wall of the core member, and that the metal line is fitted into the groove when wound around the core member.
It is preferable that anticorrosive metal be employed for the metal line.
Preferably, the envelope members are integrally formed by molding resin or rubber on the outer wall of the electrode member.
Preferably, the sensitivity of the load sensor used to detect the load is adjusted by altering, at least, one of the interval between the envelope members for enclosing the electrode member, the width in the longitudinal direction of the electrode member, the distance between the metal, coil-like wound line and the elastic tube, the thickness of the elastic tube, and the outer diameter of the elastic tube.
Preferably, the signal extraction line is electrically connected, directly or via a predetermined conductive member, to the conductive portion that is positioned at one or both ends of the elastic tube, and to the electrode members that are positioned at one or both ends of the insertion member.
It is preferable that at both ends of the elastic tube the inner space of the elastic tube be protected from the outside by predetermined shielding means.
Preferably, the insertion means is divided into two segments at a specific location in the longitudinal direction.
Preferably, the two segments are positioned at a predetermined interval.
Furthermore, to achieve the objective, it is characterized by comprising: one or multiple load sensors according to one of second, nineteenth and twenty-seventh aspects; and an insulating base member whereon one or a multiple of the load sensors are mounted.
Preferably, the load sensors are securely fixed to the base member at the ends of the load sensor or at portions whereat the envelope members are inserted between the insertion member and the elastic tube.
Preferably, the base member is a sheet member, and one or a multiple of the load sensors and the base member constitute a sheet unit. The sensor unit includes the sheet unit and a sheet-shaped insulating bag member in which the sheet unit is included.
To achieve the objective, an insertion detection device, which detects the insertion of a foreign object when an opening is closed by an opening/closing member, comprises:
a load sensor according to one of nineteenth to twenty ninth aspects, which is provided on the inner wall of the opening or the outer wall of the opening/closing member that is opposite the inner wall; and
a detector, for detecting the insertion of a foreign object by determining whether the conductive portion of the elastic tube is electrically connected to the electrode members of the insertion member via a predetermined signal line.
To achieve the above object, it is characterized by comprising:
an elastic tube, at least one part of which, in the circumferential direction, is a conductive portion;
an elongated insertion member, which has an electrode member provided longitudinally and which is inserted into the elastic tube;
envelope members, which are provided longitudinally at predetermined intervals to enclose the insertion member, and are inserted together with the insertion member into the elastic tube to separate the insertion member from the elastic tube; and
a metal conductive line, laid in the longitudinal direction of the elastic tube,
wherein the electrode member is located at a distance from the conductive portion of the elastic tube while the elastic tube is in the normal state, so that when the flexible elastic tube is bent by the application of an external load, an electrical connection is established by the electrode member, through or apart from the conductive portion of the elastic tube, and
wherein the metal conductive line is so arranged that, when the elastic tube is bent by the external application of a load, at least the portion of the metal conducive line at the load application position is capable of being electrically connected to the conductive portion of the elastic tube.
Preferably, the arrangement of the metal conductive line is such that the line can directly contact the conductive portion of the elastic tube at individual longitudinal points.
Preferably, the load sensor further comprises:
an exterior tube, which is provided on the outer wall of the elastic tube to accommodate the elastic tube and which has, at the least, one circumferential part that faces the conductive portion of the elastic tube and that serves as a conductive portion,
wherein the metal conductive line is provided so as to directly contact the conductive portion of the exterior tube at the individual longitudinal points, and
wherein the metal conductive line can be electrically connected to the conductive portion of the elastic tube through the conductive portion of the exterior tube.
It is preferable that the electrode member be fashioned from flexible members, and that the electrode member constitute the insertion member.
Preferably, the electrode member has metal, longitudinally laid lines.
Preferably, the electrode member includes an elongated flexible core member and a metal line wound coil-like around the outer wall of the core member.
It is preferable that the core member be an insulating member of resin, rubber or a fibrous material, or a compound material incorporating several of these materials.
Preferably, the core member is formed of an elastic material, and the metal line is wound around and embedded in the outer wall of the core member.
It is preferable that a spiral groove into which the metal line is to be fitted is formed in the outer wall of the core member, and that the metal line is fitted into the groove when wound around the core member.
It is preferable that anticorrosive metal be employed for the metal line.
Preferably, the envelope members are integrally formed by molding resin or rubber on the outer wall of the electrode member.
To achieve the objective, an insertion detection device, which detects the insertion of a foreign object when an opening is closed by an opening/closing member, comprises:
a load sensor according to one of first to eleventh aspects, which is provided on the inner wall of the opening or the outer wall of the opening/closing member that is opposite the inner wall; and
a detector, for detecting the insertion of a foreign object by determining whether the conductive portion of the elastic tube is electrically connected to the electrode member of the insertion member via a predetermined signal line.